Various techniques used to build a water-powered hammer or “monjolo”.
I like the technique he uses to bore the hole in the log and make the trough: hot coal, blow pipe to make it hot, clay to protect the edges and direct the burning.
The key is finding out where the balance point of a log is (might not be the center, logs taper) after gouging out the water-catching trough on the back side.
As the trough fills with water it tips the log and spills the water all at once and the log’s other end falls.
Many different technologies and ideas involved in this brilliant machine. No doubt it took quite a bit of trial and error to get it right.
I’ve seen similar pieces of technology in Japanese gardens (in Japan and in Los Angeles) called Shishi-odoshi.
[via The Kid Should See This]